NEGATIVE ABSORPTION COEFFICIENT OF A WEAK ELECTROMAGNETIC WAVE CAUSED BY ELECTRONS CONFINED IN RECTANGULAR QUANTUM WIRES IN THE PRESENCE OF LASER RADIATION MODULATED BY AMPLITUDE

2014 ◽  
Vol 38 ◽  
pp. 73-82 ◽  
Author(s):  
Nguyen Thi Thanh Nhan ◽  
Dinh Quoc Vuong
Keyword(s):  
Electromagnetic Wave ◽  
Laser Radiation ◽  
Absorption Coefficient ◽  
Quantum Wires ◽  
Negative Absorption ◽  
Rectangular Quantum Wires

Effective Dielectric Function of Porous Silicon: the Transverse Component

1994 ◽  
Vol 358 ◽  
Author(s):  
G. Gumbs
Keyword(s):  
Absorption Spectrum ◽  
Absorption Coefficient ◽  
Electron Density ◽  
Quantum Wires ◽  
Interband Transition ◽  
Incident Light ◽  
Transverse Component ◽  
Effect Of Temperature ◽  
High Electron ◽  
Confining Potential

ABSTRACTA self-consistent many-body theory is developed to study the effect of temperature and electron density on the interband absorption coefficient and the frequency-dependent refractive index for an array of isolated quantum wires. The peaks in the absorption coefficient correspond to interband transitions resulting in the resonant absorption of light. The oscillations in the derivative spectrum are due to the quantization of the energy levels related to the in-plane confining potential for such reduced dimensional systems. There are appreciable changes in the absorption spectrum when the electron density or temperature is increased. One interband transition peak is suppressed in the high electron density limit and the thermal depopulation effect on the electron subbands can be easily seen when the temperature is high. We also find that the exciton coupling weakens the shoulder features in the absorption spectrum. This study is relevant to optical characterization of the confining potential and the areal density of electrons using photoreflectance. By using incident light with tunable frequencies in the interband excitation regime, contactless photoreflectance measurements may be carried out and the data compared with our calculations. By fitting the numerical results to the peak positions of the photoreflectance spectrum, the number of electrons in each wire may be extracted.

Electromagnetic-wave-pumped free-electron laser in a plasma channel

1997 ◽  
Vol 58 (4) ◽  
pp. 613-621 ◽  
Author(s):  
JETENDRA PARASHAR ◽  
H. D. PANDEY ◽  
A. K. SHARMA ◽  
V. K. TRIPATHI
Keyword(s):  
Electron Beam ◽  
Electromagnetic Wave ◽  
Laser Radiation ◽  
Laser Pulse ◽  
Free Electron Laser ◽  
Relativistic Electron Beam ◽  
Plasma Channel ◽  
Beam Quality ◽  
Coherent Radiation ◽  
Millimetre Wave

An intense short laser pulse or a millimetre wave propagating through a plasma channel may act as a wiggler for the generation of shorter wavelengths. When a relativistic electron beam is launched into the channel from the opposite direction, the laser radiation is Compton/Raman backscattered to produce coherent radiation at shorter wavelengths. The scheme, however, requires a superior beam quality with energy spread less than 1% in the Raman regime.

Sign in / Sign up

Export Citation Format

Share Document